614 REMEDIAL MEASURES 



Trap-crops, vegetation belts, etc. A successful way of ward- 

 ing off an attack by insects of an omnivorous nature, is to sow a 

 quick-growing crop intermixed with the main crop ; thus the 

 former, furnishing food for the insects, will attract their attention 

 from the latter. Locusts are sometimes destroyed in large masses 

 by planting belts of quick-growing shrubs (such as the Castor-oil 

 plant), which at the season of the locust attack are heavily poisoned 

 by a strong insecticide, such as arsenic compounds. 



Insect traps. Trenches or holes cut in the earth are sometimes 

 found to be successful as traps for caterpillars, which, falling into 

 these at night, are unable to climb out again, and at daylight may 

 be collected and destroyed. Empty jam tins sunk level with the 

 surface soil will form good pitfalls. Also large leaves or pieces 

 of cut vegetation laid on the ground act as useful traps, as many 

 injurious insects will hide under these during part of the day, 

 especially in the early morning, when they should be looked for 

 and destroyed. 



Mechanical protection against insect pests. In spite of all 

 precautionary measures it is often necessary, especially in up- 

 country gardens, to protect young tender seedlings by placing a tin 

 cylinder around each plant until it has outgrown its liability to be 

 attacked by grubs, etc. These tin "collars" may be obtained 

 locally at about Rs. 2 per hundred. Empty jam and condensed- 

 milk tins, or even a roll of stout paper, may also be used for 

 the purpose. 



Plants as insect-preventives. Certain plants have the re- 

 putation of possessing properties which are obnoxious to insects, 

 and of having the effect of driving the latter away. Thus tomato 

 leaves are, in some countries, spread around tender plants, and by 

 reason of their strong odour are supposed to afford protection 

 from injurious insects. Acorus calamus ("Wada-kaha ") and several 

 species of Alocasia (" Habarala") are considered to be effective 

 against termites (white ants). Thus MR. RIDLEY, late Director of 

 Botanic Gardens, Singapore, states that the roots of the former 

 plant l are pounded to powder, spread around the base of trees 

 attacked by white-ants, when all the latter will die." (See Straits 

 Agricultural Bulletin for 1904). Cultivators of market gardens 

 up-country use the chopped-up leaves of the " Wild Lobelia " or 

 Kiri-bamboo " (Lobelia nicotianifolia) as a protection from the 

 destructive black-grub, while in the low-country tobacco leaves 

 are considered by some to have a deterrent effect on certain 

 insects. 



